1. Field of Invention
This invention relates to contour measuring apparatuses.
2. Prior Art
A contour measuring apparatus of the prior art comprises a stylus adapted to be moved in contact with the outer surface of an object to be measured, a support arm for the stylus, a slider vertically movably supporting the support arm relative to the outer surface of the object and horizontally movable, a differential transformer detecting the vertical displacement of the support arm, a screw shaft for horizontally moving the slider and a motor driving the screw shaft. In general, it has been usual practice that the contour measuring apparatus is used together with a recorder such as a pen recorder. In that case, the recording paper feeding on the recorder is turned in synchronism with the motion of the slider of the contour measuring apparatus and the pen of the recorder is adapted to be driven in accordance with the output of the differential transformer of the contour measuring apparatus.
To keep the movement of the paper feeding on the recorder in synchronism with the motion of the slider of the contour measuring apparatus, synchronizing motors are used as the motor of the contour measuring apparatus and the paper feed motor. Accordingly, as viewed from a common sense approach, the motor of the contour measuring apparatus and the paper feed motor should be in perfect synchronism. However, in reality, a gear train is interposed between the motor of the contour measuring apparatus and the screw mechanism for driving the slider and the irregularities in the rotation of these gears resulted in a nonuniform speed motion of the slider and the stylus which causes a difficulty.
Moreover, the contour measuring apparatus known in the art is of such a construction that the slider supporting the stylus cannot be manually operated. Even if manual operation were performed, the paper feeding the recorder or the motion of the pen does not occur in the case of manual operation and hence the recording of the contour measured by manual operation is impossible. Furthermore, the prior art contour measuring apparatus is not capable in the automatic mode of measuring the contour of the small object. In addition, the backlash between the feed screw shaft and the transferrable member threadably coupled to the feed screw shaft in the prior art contour measuring apparatus introduces additional errors in the values measured by the contour measuring apparatus.